export let vertexShaderSource = `
      attribute vec4 a_position;
      attribute vec3 a_color;
      
      // 世界矩阵
      uniform mat4 u_world;
      uniform mat4 u_unit;
      varying vec3 v_color;
      
      void main (){
        gl_Position = u_world * u_unit * a_position;
        v_color = a_color;
      }
`
